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Archived: What is the Maximum Buffer Size that I Can Configure for My DAQ board?

This document has been archived and is no longer updated by National Instruments

Note: This page is about NI-DAQ also known as Traditional NI-DAQ (Legacy). NI-DAQmx replaced Traditional NI-DAQ (Legacy) in 2003. NI strongly recommends using NI-DAQmx for new designs and migrating existing Traditional NI-DAQ (Legacy) applications to NI-DAQmx. Please review the Getting Started with NI-DAQmx guide for more information on migration.


Hardware: PXI/CompactPCI>>Controllers

Problem:
I am using Traditional NI-DAQ's AI Config.vi in LabVIEW to configure my DAQ board for analog input. What is the maximum value that my board can use for the AI Config buffer size input parameter?

Solution:
Before starting a transfer of data from your DAQ card to your PC, NI-DAQ needs to allocate a buffer to hold the data and lock that buffer into your PC’s physical memory. The buffer size input parameter on AI Config.vi determines the size of the PC memory buffer that you want to allocate for data acquisition. This is independent of size of your DAQ card’s onboard buffer. The default setting for this input is 1000 scans; however, the limit for this is not absolute.

NOTE: There is a bug in Windows NT that does not allow more than 32 MB of memory to be allocated at once, and a bug in some versions of Windows 95 (e.g., version 4.00.1111) that does not allocate buffers in the 100 KB to 1 MB range (approximately). This is reported in CAR 17PDPIJV.



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Report Date: 09/18/2000
Last Updated: 03/06/2009
Document ID: 21H93SYF

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